The invention relates to a method of shutting down a pluggable electrical unit in a modular system.
Complex electrical engineering systems, in particular in measuring and control technology and in telecommunications, are often of a modular construction. This involves a large number of electrical units being accommodated in an enclosure of an electrical base unit in a pluggable manner. The pluggable electrical units are mechanically of an identical construction but electrically different according to their intended function.
The unprepared removal of one of the pluggable electrical units from a complex system of this type while operation is in progress gives rise to the risk of disruption to the units remaining in operation, as a consequence of the uncontrolled interruption of communication operations which are in progress, since one of the communication parties suddenly and unexpectedly no longer responds.
EP 373 773 discloses a method of removing a plug-in card in which the plug-in card is put into a state of reduced power consumption before its physical removal from the system by applying a predetermined clock signal.
EP 548 382 discloses a method of accomplishing assembly exchange operations while a bus system is in operation, in which system a slot control unit is informed of the imminent assembly exchange operations via a console and the bus system or via a serial interface. The entire bus system is switched by means of the slot control unit into a state in which it is free of bus accesses. It is disadvantageous that the bus traffic is interrupted for all the assemblies during the entire time of the assembly exchange operations.
The known methods share the feature that an imminent removal of an assembly has to be reported manually and separately to the system by an operator and it is subsequently necessary to wait until the system signals readiness for the removal of the assembly.
The invention is therefore based on the object of specifying a method of shutting down a pluggable electrical unit in a modular system which manages without a separate announcement of the imminent removal and avoids interruption of the bus traffic for units remaining in the system.
The invention is based on a modular system comprising a base unit and at least one pluggable electrical unit, each pluggable electrical unit having at least one set of module electronics and a switch, which is coupled to a mechanical locking of the pluggable electrical unit in the base unit. The interface between the base unit and the pluggable electrical unit is provided with a variable resistor, arranged in the feed line, and switching means, via which the module electronics are communicatively connected to the base unit.
The essence of the invention is that the obligatory actuation of the switch in the pluggable electrical unit to be removed initiates a process in which the power supply is switched off only for the pluggable electrical unit to be removed, and the communicative connection between the pluggable electrical unit to be removed and the base unit is interrupted.
Because of the mechanical unlocking which has to precede the physical removal of the pluggable electrical unit and the associated obligatory actuation of the switch, it is possible to dispense with separate reporting of the imminent removal of the pluggable electrical unit.
When a pluggable electrical unit is removed, a handling time in the range of several seconds from the actuation of the switching contact to the actual disconnection of the contacts of the plug-in contact device elapses. Given a minimal time which the modular system requires to take into account the imminent removal, of the order of magnitude of a few hundred milliseconds, the system is reliably able to have taken all the required precautions before the corresponding pluggable electrical unit has been physically removed from the system.
This involves terminating communication operations which are in progress and subsequently interrupting the communicative connection between the pluggable electrical unit to be removed and the base unit via the switching means. The communication connections between all the units remaining in the system are in this case continuously maintained. This avoids disruptions in the system.